Fiber-foam shoe insoles, and a method of manufacturing the same

ABSTRACT

This document discloses antistatic shoe insoles that include a flexible foam layer and antistatic filaments of textile material interspersed throughout the foam layer and extending passed or exposed at the surface of the shoe insole and methods of making such an antistatic shoe insole. The antistatic filaments are needle punched through the foam layer. The antistatic filaments may be any suitable antistatic material blended with any felt fiber such as wool fiber, cotton fiber, polyester fiber, or the like.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/920,167 filed Jul. 2, 2020, which claims the benefit of U.S. PatentApplication Ser. No. 62/870,296, filed Jul. 3, 2019 entitled “ANTISTATICFIBER-FOAM SHOE INSOLES, AND A METHOD OF MANUFACTURING THE SAME,” eachof which is incorporated by reference herein in its entirety.

FIELD OF INVENTION

The present invention relates to antistatic shoe insoles and a methodfor manufacturing antistatic shoe insoles which includes a flexible foamlayer and antistatic filaments of textile material substantiallyuniformly interspersed throughout the foam layer and extending passed orexposed at a surface of the shoe insole.

BACKGROUND

With modern technology, various industrial products need to be producedand/or operated in highly controlled environments and electrostaticcharges in those environments can impair the quality and operation ofsuch products. For example, if the charges accumulate to a hazardouslevel, electrostatic discharge may lower the quality of the products andeven cause related industrial hazard, such as an electric shock.

For example, electrostatic discharge events cost the electronicsindustry billions of dollars annually. These costs are attributable tothe requirement for replacing damaged and inoperable equipment that hasbeen affected by electrostatic discharge, as well as the downtime causedby these failures. As a result, electrostatic discharges should beminimized or eliminated whenever possible. One of the more commonelectrostatic discharge events to occur is when a person simply walksacross the surface of the floor. In this example, static electricity isgenerated when the wearer's shoe soles touch and then separate from thefloor while in motion.

This can happen when two dissimilar materials rub together, staticelectricity arises creating an electrical charge and an imbalance ofpositive and negative charges. During this rubbing, friction causespositive charges to accumulate on one surface, and negative charges onthe other. When the materials are acceptable conductors of electricity,the charges are readily dissipated away. However, in instances where thematerials are not acceptable conductors of electricity, an unpleasant,and perhaps dangerous, electrical discharge may occur which results instatic electric shock. This static electric shock can negatively impactpeople and it has the very real potential to severely damage electronicequipment, which is highly susceptible to static electricity. Therefore,different kinds of antistatic equipment and devices were inventedincluding antistatic shoes.

When used in conjunction with electrostatic discharge flooring,antistatic shoe insoles and footwear are a very reliable method ofeliminating static charge from personnel and work environments. Anexample of this is when the electrical charge passes from the wearer'sfeet, down through the antistatic shoe insole and out of the wearer'sshoe to the floor. Rather than electrical charge being discharged intosensitive electronic equipment, the charge which builds up on wearer isinstead passed to the floor and dissipated safely. In sum, antistaticshoe insoles and electrostatic discharge footwear are designed to ensureconstant drainage of static charges from the body to the floor. For theantistatic and ESD shoes to be effective, both the shoe insoles and theshoes themselves must be ESD rated to provide continuous electriccontact of the foot to ground as required by global ESD standards.

However, current antistatic and/or ESD shoes commonly contain shoeinsoles that have a thick, single stitch of conductive fiber in the toesection that the wearer can visually see and physically feel on the topsurface of the shoe insole. This aforementioned thick, single stitch ofconductive fiber of the current antistatic and/or ESD shoe insoles ofmention is known to be uncomfortable for the wearer as it can bephysically felt directly under-foot as it can come in direct contactwith the wearer's toes. The wearers discomfort from wearing the currentantistatic and/or ESD shoe insoles of mention is exacerbated by the factthat the shoe wearer often wears their antistatic and/or ESD shoes formany hours at a time in industrial work environments. The prolongedperiods of use by the wearer with the current antistatic and/or ESD shoeinsoles can greatly increase the chances for blisters on the wearer'sfeet, as well as increases the chances of foot bruising caused by footfatigue from excessive use. Thus, there is a continuing need for animproved antistatic and/or ESD shoe insole that the instant inventionprovides a suitable solution for in terms of both improved comfort tothe wearer and in terms of a higher degree of static electricdissipation per capita.

SUMMARY OF INVENTION

The present invention is directed to antistatic shoe insoles whichinclude a flexible foam body with an antistatic layer and antistaticfilaments uniformly interspersed throughout the foam body. Morespecifically, an antistatic insole comprises a flexible foam body withan antistatic felt layer disposed on top of the flexible foam body,where a plurality of filaments of the antistatic felt layer are embeddedin the flexible foam body. In some embodiments, the foam body is apolyurethane (PU) foam, but can be any other suitable flexible foam, andthe antistatic layer is made of a blend of a non-woven textile with anantistatic additive. The antistatic additive can be composed ofconductive fibers to allow for the dissipation of the static electriccharge. Further, the insoles have a portion of the filaments extend passa bottom surface of the shoe insole so as to be exposed exteriorly.

Unlike the current antistatic and/or ESD shoe insoles of mention, theinstant invention has a smooth top surface whereby the wearers feet donot contact any stitching or uncomfortable surface changes; essentially,the wearer cannot feel any difference between a standard non-anti-staticand/or ESD shoe insole and that of the instant invention under foot, andthis greatly improves the comfort of the instant invention for the shoewearer over the current antistatic and/or ESD shoe insoles. Anotheradvantage of the instant invention over the current antistatic and/orESD shoe insoles, and that of the prior art, is that the instantinvention provides a greater amount of conductive fibers per squarecentimeter, covering nearly the entire top and bottom surface, and thisgreatly improves the static dissipation capability over the prior art,thereby making it more efficient and reliable in use, especially overprolonged periods of use.

The present invention, in another aspect, is directed to a process formanufacturing antistatic shoe insoles which include a flexible foamlayer and antistatic filaments of a textile material substantiallyuniformly interspersed throughout the foam layer and extending past orexposed at the surface of the shoe insole. In some embodiments, themethod comprises disposing an antistatic felt layer on top of a flexiblefoam body, where the antistatic felt layer is a blend of a non-woventextile with an antistatic additive, and penetrating filaments of theantistatic layer into the flexible foam body, wherein the filaments areembedded into the foam body and a portion of the filaments extend to abottom working surface of the foam body as to be exteriorly exposed. Theantistatic filaments are optimally needle punched through the foam layerusing a needle loom. In the method, a needle loom oscillates a needleboard into the foam body with the antistatic felt layer. During theoscillation, the needles grab hold of portions of the antistatic layerand punch filaments of the antistatic felt layer into the foam body suchthat a portion of the filaments extend to a bottom working surface ofthe foam body as to be exteriorly exposed. This exposure of theantistatic filaments is what dissipates the electrical static dischargethrough the shoe wearer's feet, into and out of the sole insole, andsafely out to the floor.

The details of one or more embodiments are set forth in the accompanyingdescription below. Other features and advantages will be apparent fromthe description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an antistatic insole,in accordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional view of the embodiment of FIG. 1 ;

FIG. 3 is an illustration depicting a flexible foam body used in anantistatic insole, in accordance with an embodiment of the presentinvention;

FIG. 4 is an illustration depicting a first step of manufacturing anantistatic fiber-foam insole, in accordance with an embodiment of thepresent invention;

FIG. 5 is an illustration depicting a second step of manufacturing anantistatic fiber-foam insole, in accordance with an embodiment of thepresent invention;

FIG. 6 is illustration depicting a cross-sectional view of an antistaticinsole during a second step of manufacturing an antistatic fiber-foaminsole, in accordance with an embodiment of the present invention; and

FIG. 7 is cross-sectional view an antistatic insole, in accordance withan embodiment of the present invention.

DETAILED DESCRIPTION

As illustrated in FIG. 1 , an antistatic shoe insole 2 includes a mainbody portion 4 which is comprised of a flexible foam body 16. The bodyportion 4 has a bottom working surface 8 and a top surface 12. As isknown in the art, in some embodiments, the shoe insole 2 can beconstructed to be double sided such that the top surface and the bottomworking surfaces will appear to be the same. In other embodiments, thetop surface and bottom working surface may be different materials toensure the optimal comfort and design for the shoe wearer. Severalnon-limiting examples of the top surface of the instant invention can beany conductive woven or non-woven material such as a steel-polyesterfelt blend or carbon-containing fibers, while several non-limitingexamples of the bottom working surface of the instant invention can becomprised of any conductive woven or non-woven material such as silvercoated fibers or fine inox wire. In other embodiments, there can be anoptional cover layer disposed on top of the antistatic felt layer. Forexample, any suitable woven, knitted, or non-woven fabric may beoptionally used as a cover layer provided that it has adequateantistatic properties. The cover layer can be made of an antibacterialmaterial, a microbial material, a moisture wicking material, or anyother suitable material that has inherent antistatic dissipationproperties.

In some embodiments, the foam body 6 is comprised of an open-cellpolyurethane foam (PU), both other suitable materials such as aclosed-cell ethylene vinyl acetate (EVA) foam may also be used. Stillfurther, in certain embodiments, the foam body 6 is comprised of anon-woven fiber batting made from elastomeric polyester or the like thatcan substitute conventional foams known in the art.

The antistatic shoe insole 2 further comprises a layer of antistaticfelt 18 disposed on top of the foam body 6, as shown in FIGS. 1-2 . Theantistatic felt layer 18 forms the top surface 12 of the antistaticinsole 2. The antistatic layer 18 comprises a blend of a textile fabricwith an antistatic additive. For example, in some embodiments, theantistatic layer 18 is made of a blend of steel fibers in a polyesterfabric. In other embodiments, depending on the use of the antistaticinsole 2, the antistatic layer 18 can comprise a natural textile fabricsuch as cotton, wool, jute, hemp, and even more advanced naturalmaterials such as polylactic acid, or bionylon blended with theantistatic additive. In the antistatic layer 18 the antistatic additivecomprises at least 1% percent by weight. In other embodiments, theadditive may range from 1 to 50 percent by weight, and more preferablymay range from between 5 to 20 percent by weight. The antistaticadditive can be steel fibers, carbon-containing fibers, silver coatedfibers, fine inox wire, or any other suitable conductive fiber.

As illustrated in FIG. 2 , the insole 2 further includes filaments 24 ofthe antistatic layer 18 penetrating through the flexible foam body 6.The filaments 24 are embedded into the foam body a given depth such thatan end portion 24 a of the filaments 24 extend to the bottom workingsurface 8 of the foam body so as to be exteriorly exposed. This exposureof the antistatic filaments 24 permits electrical static discharge to bedissipated through the shoe wearer's feet, into and out of the soleinsole, and safely out to the floor.

In other embodiments, the present invention is directed to a method ofmanufacturing an antistatic insole. In some embodiments, the methodcomprises disposing an antistatic felt layer on top of a flexible foambody, where the antistatic felt layer is a blend of a non-woven textilewith an antistatic additive, and penetrating a plurality of filaments ofthe antistatic layer into the flexible foam body, wherein the filamentsare embedded into the foam body and a portion of the filaments extend toa bottom working surface of the foam body so as to be exteriorlyexposed. FIGS. 3-7 illustrate the various steps in one embodiment of amethod of manufacturing an antistatic shoe insole in accordance with thepresent invention. Initially, a flexible foam body 16 is provided. Thefoam body 16 may be a sheet of foam while in other instances it may be acontinuous sheet of foam that may be fed from a roll or the like.

Preferably, the foam body 16 is comprised of open-cell PU foam but othersuitable materials such as closed-cell EVA foam may also be used. Thedensity of the foam 16 will be selected as desired for the particularpurpose for which the antistatic shoe insoles 2 may be used.

In a first step, an antistatic layer 18 is disposed on the foam body 16as shown in FIG. 4 . The antistatic layer 18 is a non-woven fabricformed with an antistatic additive (i.e. a conductive material). Theantistatic layer 18 comprises a blend of textile fibers with conductivefibers. For example, in some embodiments, the antistatic layer 18 ispreferably made from a blend of steel fibers and polyester fibers Inother embodiments, depending on the use of the antistatic insole 2, theantistatic layer 18 can comprise a natural textile fabric such as cottonor wool, jute, hemp, and even more advanced natural materials such aspolylactic acid, or bionylon blended with the antistatic additive. Theantistatic additive can be steel fibers, carbon-containing fibers,silver coated fibers, fine inox wire, or any other suitable conductivefiber.

In the antistatic layer 18 the antistatic additive comprises at least 1percent by weight. In other embodiments, the additive may range from 1to 50 percent by weight, and more preferably may range from between 5 to20 percent by weight. The antistatic additive can be steel fibers,carbon-containing fibers, silver coated fibers, fine inox wire, or anyother suitable conductive fiber.

Like the foam body 16, the antistatic layer may be a sheet, as shown inFIGS. 4 and 5 , while in other instances it may be fed from a continuousroll onto the foam 16. In some embodiments, the antistatic layer 18 canbe optionally affixed to the foam 16 through the use of an appropriateadhesive to insure a secure bond therebetween. In other embodiments, theantistatic layer 18 may be affixed to the foam body by stitching or anyother suitable method.

Following step 100, in step 200, filaments 24 of the antistatic layer 18are embedded into the foam body 16, as shown in FIGS. 6 and 7 . To embedthe filaments 24 into the foam body 16, a needle punch or needle loomingprocess is performed. The needle loom works by in-feeding the foam body16 with the antistatic layer 18 into a needle looming machine. The foambody and the antistatic layer, layered like a sandwich, are fed into theneedle loom by an automatic conveyor belt that introduces the two layersto the needle board in oscillation.

With the antistatic layer 18 overlying the foam body 16, the combinedstructure is then placed under a plurality of needles 20, each of whichcarries a plurality of downwardly extending barbs 22, seen in FIG. 5 .The needles 20 and barbs 22 are used to produce what is commonlyreferred to as needle punched felt and similar materials, which areknown in the art. The needle loom oscillates the needle board into thefoam body and antistatic layer sandwich a given thickness. Essentially,the barbs 22 on the needles 20 grab a hold of portions of the antistaticlayer 18 and punch filaments 24 of the antistatic layer 18 into the foambody 16. The typical needle penetration is 12 mm to 15 mm but can beadjusted depending on the thickness of the foam body 16. The needles 20penetrate a sufficient depth to carry the filaments 24 through thecombined thickness of the antistatic layer 18 and the foam body 16 tocreate a mechanical bond between the foam body 16 and antistatic layer18. Further, the needles penetrate a sufficient depth to such that aplurality of end portions 24 a of the filaments extend to the bottomworking surface of the foam body so the portions 24 a are exteriorlyexposed.

As shown in FIG. 6 , as the needles 20 are moved downwardly through theantistatic layer 18, the barbs 22 catch a plurality of filaments 24 anddraw them downwardly into the foam 16 so that the filaments 24 extendfrom the top surface 12 as shown in FIG. 2 and through the foam 16 asshown in FIG. 6 . Preferably, the ends of the fibers are drawn passedthe bottom surface 8 of the foam 16 so as to be exposed at and extendbeyond the working surface 8. The needles 20 are then raised. However,the elongated filaments 24 are entangled within and remain in the foamas shown in FIG. 7 .

This process can be repeated as many times as desired in order toincrease the density of the antistatic filaments 24 relative to the foambody 16. To do so, after the needles 20 are raised, the combinedantistatic layer 18 and foam body 16 are shifted within the needle loomand the needles 20 are then again moved downwardly to penetrateadditional filaments 24 from the antistatic layer 18 into the foam 16.Thus, the density of the filaments 24 relative to the foam body 16 is afunction of the number of needles 20, the speed of movement of theantistatic layer 18 and foam 16 under the needles 20 and the frequencyof the up and down strokes of the needles 20.

After the antistatic filaments 24 are needle punched into and throughthe foam body 16 as shown in FIG. 7 , the composite structure can be cutto the desired shoe insole shape, a finishing step 300, to form anantistatic shoe insole. If a single sided antistatic shoe insole isbeing produced, a cover layer can be secured on top of the antistaticlayer 18. If a double-sided antistatic shoe insole is to be produced,the antistatic layers 18 of two antistatic fiber injected sheets will besecured together with adhesive in between them, as is well known in theart. As should be apparent, the final antistatic shoe insoles can be cutinto the proper shape before or after they are assembled.

Although a few embodiments have been described in detail above, othermodifications are possible. Other embodiments may be within the scope ofthe following claims.

What is claimed is:
 1. A antistatic shoe insole comprising: a flexiblefoam body having a top surface and a bottom working surface; and afabric layer positioned on the top surface of the foam body, the fabriclayer including a plurality of filaments forming a mechanical bondbetween the fabric layer and the flexible foam body and extending fromthe fabric layer and through the flexible foam body, and wherein aportion of the plurality of filaments of the fabric layer extend to thebottom working surface of the foam body and are exposed exteriorlythrough the bottom working surface.
 2. The shoe insole of claim 1,wherein the flexible foam body is comprised of an open-cell polyurethanefoam.
 3. The shoe insole of claim 1, wherein the flexible foam body iscomprised of a closed-cell ethylene-vinyl acetate foam.
 4. The shoeinsole of claim 1, wherein the fabric layer is an antistatic layercomprising a blend of a non-woven textile with conductive fibers.
 5. Theshoe insole of claim 4, wherein the conductive fibers comprise at least1% by weight of the fabric layer.
 6. The shoe insole of claim 4, whereinthe conductive fibers range from 5% to 20% by weight of the fabriclayer.
 7. The shoe insole of claim 1, wherein the fabric layer is anantistatic layer comprising a blend of polyester fabric with a pluralityof steel fibers.
 8. The shoe insole of claim 1, wherein at least aportion of the plurality of filaments are entangled within the foambody.
 9. The shoe insole of claim 1, wherein the fabric layer isstitched to the flexible foam body.
 10. The shoe insole of claim 1,wherein the fabric layer includes a natural textile fabric.
 11. The shoeinsole of claim 10, wherein the fabric layer is comprised of cotton,wool, jute, hemp, polylactic acid, and/or bionylon.
 12. The shoe insoleof claim 1, wherein the fabric layer includes a felt material.
 13. Theshoe insole of claim 1, wherein the fabric layer is configured to bepositioned between a user's foot and the flexible foam body when theshoe insole is worn by the user.
 14. The shoe insole of claim 1, whereinthere is no adhesive coupling the fabric layer to the flexible foambody.